$fColor: cornflowerblue;

*,
*:before,
*:after {
    box-sizing: border-box;
    margin    : 0;
    padding   : 0;
}

h1 {
    font-size    : 1em;
    padding      : 0.5em;
    border-bottom: 1px dashed $fColor;
    color        : $fColor;
    cursor: pointer;
}

.container {
    display    : flex;
    flex-flow  : row nowrap;
    height     : 100vh;
    align-items: stretch;

    .ctrl {
        border-right: 1px dashed $fColor;
        flex        : 400px 0 1;
    }

    .prev {
        flex: 600px 3 1;
    }
}